[FIXED] Understanding the use of any() and all() in numpy arrays

Issue

What's the difference between the following:

a = np.array([2,3,4])
b = np.array([2,7,8])

if a.any() == b.all():
   print('yes')

and

a = np.array([2,3,4])
b = np.array([2,7,8])

if a.any() == b.any():
   print('yes')

In both situations, 'yes' is printed.

Solution

any() and all() are intended for boolean arrays. any() returns True if there's any values that are equal to True in the array. all() returns True if all values in the array are equal to True. For integers/floats the functionality is similar, except that they return True if the value 0 is not found in the array. In your example, since both a.any() and a.all() will return True, it follows that a.any() == a.all().

Try executing the following code to see how it works in practice.

a = np.asarray([1,2,3])
b = np.asarray([-1,0,1])
c = np.asarray([True, False])

print(a.any())
print(a.all())

print(b.any())
print(b.all())

print(c.any())
print(c.all())

Answered By - user2653663